Electrochromism is a phenomenon in which a material exhibits a reversible electrochemically-mediated change in an optical property when placed in a different electronic state, typically by being subjected to a voltage change. The optical property is typically one or more of color, transmittance, absorbance, and reflectance. Electrochromic devices may be incorporated into many types of optical structure including windows and mirrors. The optical state of such devices is switched by an electrochemical transition.
One well known electrochromic material is tungsten oxide (WO3). Tungsten oxide is a cathodic electrochromic material in which a coloration transition, transparent to blue, occurs by electrochemical reduction.
While electrochromism was discovered in the 1960s, electrochromic devices still unfortunately suffer various problems and have not begun to realize their full commercial potential. Part of the difficulty is a lack of versatility in the operating modes of electrochromic devices. Additionally, known control systems for electrochromic devices have limited functionality and fail to account for some of the unique features of electrochromic devices.